A conventional liquid crystal display (LCD) includes an LCD panel and a backlight module. Because the LCD panel cannot actively emit light, the backlight module is required to be as a light source. The backlight module includes a backlight source, a back cover, a light guide plate (LGP), a reflector, a diffuser, a brightness enhancement film (BEF), and other optical films. A cold cathode fluorescent lamp (CCFL) and a light emitting diode (LED) are commonly used as light sources for the backlight module. Since the LED has more advantages such as low power consumption, long lifespan, no mercury additives and other advantages, the LED is gradually replacing CCFL to be a mainstream backlight source.
According to the placement location of the backlight source, the backlight modules can be generally categorized into the following types: a direct type backlight module and an edge-lit backlight module. The direct type backlight module has the light sources disposed on the back of the backlight module. The edge-lit backlight module has the light sources disposed on the sides of the light guide plate, and the light guide plate guides the light to pass through the light guide plate to the back of the LCD panel. Similarly, the backlight modules that utilize the LEDs as light sources can be categorized into these types: a direct type LED backlight module and an edge-lit LED backlight module. There are two advantages of the edge-lit LED backlight module: the first advantage is the edge-lit LED backlight module uses fewer LED dice than the direct type LED backlight module so as to save costs. The second advantage is that a lighter weight LCD can be manufactured by utilizing the edge-lit LED backlight module. The edge-lit LED backlight module does not require an LED module and the cooling components to be disposed at the rear of the LCD panel, instead, they are disposed on the sides of the LCD panel. Such structure can reduce the overall thickness of the LCD, so that an LCD TV with a lighter weight can be produced in comparison to the LCD TV using the direct type LED backlight modules.
At present, due to the increasing size of a bigger screen TV, more light sources are required to provide light to the display panel. Therefore, a general four-sided edge-lit LED backlight module utilizes four LED light bars to be placed on the four edges of the screen to provide light. FIG. 1 is a perspective view of a prior art back plate having an edge-lit LED backlight module with LEDs on 4 edges. Please refer to FIG. 1, a back plate 100 includes a bottom plate 110, four lateral sides 120, 140, 160 and 180. In addition, four L-type baffles 111, 112, 113 and 114, being designed to be disposed at four corners of the bottom plate 110, are deformed from the stamping parts of the back plate 100. The four L-type baffles 111, 112, 113 and 114 are utilized to fix a light guide plate 300 onto the back plate, and the four L-type baffles are to restrict the movement of the light guide plate in order to avoid damaging the LED dice on the LED light bars (not shown) when impacting the light guide plate.
However, the conventional L-type baffles cannot ensure that the light guide plate is tightly disposed on the back plate, and this may result in loosening the light guide plate. In addition, when a shock test is proceeded on the backlight module, the LED light bars may be impacted by the loosened light guide plate. Consequently, the LED dice may be broken, hence causing the reliability of the backlight module to be reduced. Moreover, the conventional method of fixing the light guide plate is to fix with the protrusions or baffles which are produced by stamping the sheet metal of the back plate or by other material processing. However, the aforesaid material processing can also increase the production costs.
Therefore, there is an urgent need to provide a novel edge-lit backlight module to overcome the above-mentioned drawbacks.